Generally, a conventional ball chair comprises a chair base, and a ball body is connected to the chair base. Wherein the chair base formed integrally has a ring support, and a plurality of chair legs respectively protrude from the ring support. Moreover, the ball body is installed on the ring support, and a diameter of the ball body is larger than the ring support, thus completing the assembly of the ball chair which is configured to correct sitting posture or achieve physical training for a user.
However, the conventional ball chair is disadvantageous because: (i) when used, a height of the integrated conventional ball chair cannot be adjusted according to a user's statures, thus lowering the practicability thereof; and (ii) the ball body is only supported by the ring support, when a downward pressure is gradually increased, the ball body is configured to be deformed and detached from the ring support, thus increasing the risk of use. Therefore, there remains a need for a new and improved design for a ball chair to overcome the problems presented above.